1. Field of the Invention
The present invention relates to devices for conveying and dispensing liquid media such as casting resin, and in particular to such devices utilizing at least one piston pump having a cylinder chamber which forms a guide for the piston, and which is connected to a feed container and has an output for dispensing liquid from the feed container.
2. Description of the Prior Art
Various piston pumps are known in the art for dispensing liquid media, all of which have a piston seal serving as the piston guide which interfaces at one side with the atmosphere. Although it is possible to achieve a good seal by the use of, for example, elastic seals, such seals are easily attacked and destroyed by many types of liquid media which are to be conveyed and dispensed. This problem is particularly acute when the medium to be dispensed is casting resin to which fillers such as quartz sand and the like are added. Such fillers produce friction between the piston and the cylinder and thereby destroy the seals resulting in pump leaks and absorption of air.